MS16 Battery Scope & Roadmap

MS15 Brief Review

What went right?

Passed all regulations
*Reliable
It worked

Note: Reliable as in not breaking down after put into the car or being a source of failure. * asterisk is added because the BMS was not very reliable, and we ought to take some responsibility for not completing earlier so Electrical could have done more testing

What could have been better?

DFA
- Pack assembly into enclosure was difficult due to interference
- Baffles being mounted into the enclosure was difficult due to interference
- Module holders being epoxied into the enclosure floor introduced misalignment
Serviceability/Quality-of-Life
- Module series-to-series connection was difficult to do and undo
- Modules were difficult to install and remove
- Hardware mounting on top of batteries made the boards difficult to access for troubleshooting
Quality Control
- 2 modules had 0.5V-1V imbalance between parallel groupings and ~6 had 0.2V imbalance between parallel groupings, likely because we did not test for capacity. At the end, we had maybe 1 module that was suitable to be a back-up replacement, which is a lot of money spent on cells that didn’t go anywhere because we didn’t have the time to make new modules in the end.
More rigorous testing & analysis
- Due to falling behind on timeline and also some general cluelessness from inexperience, we rushed into manufacturing without having a lot of useful test data. Examples: didn’t have any data or calculations on how cooling will go, didn’t do sims on enclosure mounting into chassis, didn’t have data on actual battery pack capacity going into race, didn’t have any data on if vibrations will be an issue given lack of potting or any significant design considerations there (other than battery box sitting on pool noodles). Fortunately things went okay, but this shouldn’t happen again.

MS16 Battery Design Constraints & Requirements Overview

For MS16, we will continue with the typical requirements relating to battery design with extra emphasis being placed on DFA and serviceability.

Constraints & Requirements	Relevant Components	Description & Examples
Safety (Thermal, Electrical, Mechanical)	Thermal management Module Enclosure Cell	Ensure batteries are being used within safe operating limits (temperature, capacity) Ensure all conducting material (current collectors, busbars) will operate within a safe temperature range Mitigate likelihood of thermal run-away and thermal runaway propagation Ensure batteries are safe from damage in crash-scenarios Ensure batteries are safe during expected drive conditions (NVH, raining/wet conditions) Ensure driver safety in crash and thermal runaway scenarios Ensure operator and battery safety during servicing
Minimize weight	Module Enclosure Cell	Simplify design and do good material selection Overall MS16 weight goal is 300kg (MS15 was 440kg)
Minimize power loss/redundant power consumption	Everything	Minimize power requirement for cooling Minimize cell internal resistance and connections' contact resistance
Minimize manufacturing & assembly time (DFM/DFA)	Module Enclosure	Battery manufacturing and assembly should be complete by early Winter 2026 so that testing can be complete by EOT. Spring 2026 is hands-off for mechanical, reserved for drive testing. Reduce parts, simplify design
Minimize cost/stay within budget	Everything	Wasn’t necessarily a problem with MS15, but based on our cell funding being $2500 this year (the lowest option available, we received $5000 for MS15), it’s important to keep budget in mind. Especially since there are more design teams this year than when MS15 started.
Serviceability/Quality-of-Life	Thermal management Module Enclosure	Reduce required serviceability time for module replacement and integration with mechanical & electrical systems. Reduce possible instances where catastrophic servicing mistakes can happen. (i.e. situations where you might drop something that can damage aero, situations where you might drop something that can damage hardware boards) Improve hardware accessibility for quick trouble-shooting. Aim for accessibility while operator is outside of the car. Improve ergonomics related with servicing pack & battery hardware (somewhat of a nice-to-have, but keep in mind for design wherever we can)
Constraints & Requirements Relating to other sub-teams	Everything	Electrical: Design with hardware & firmware’s constraints & requirements. (ex. new boards? available ICs? PCB budget? ) Mechanical Design with overall mech & other mech sub-teams' constraints & requirements in mind. (ex. space claim? CoG?)
ASC Regulations	Everything	Will influence some of the above constraints & requirements ASC regulations that don’t have much to do with what’s above: Impounding regs Battery security regs

MS16 Battery Roadmap Overview

Fall 2024

Pack configuration, overall layout decided
Cell candidates (top 3) chosen
Thermal testing & cell testing process outline
New member onboarding & getting people established into long term projects
Components early ideating

Winter 2025

Cell candidate testing
- Cell testing (IR, capacity, temperature profile)
- Prototype module testing (temperature profile) IF we happen to end up testing different P counts
- Finish cell selection and make mass cell purchase
- Begin mass cell testing if possible
Enclosure official design sprint start, finish 90% of design by EOT
Module official design sprint start, finish 90% of design by EOT

Summer 2025

Finish mass cell testing (early on in the term)
Prototyping, finalize enclosure design, begin material purchasing and manufacturing
Prototyping, thermal testing, finalize module design, begin material purchasing and mass manufacturing

Fall 2025

Finish module mass manufacturing
Finish enclosure manufacturing
Begin module testing & integration

Winter 2026

Finish battery-elec integration
Begin and finish characterization of pack

Summer 2026

Drive testing finished car